Radiation-Resistant Porous Materials for Capture and Separation of Volatile Radionuclides

The release of volatile radionuclides, which must be captured and subsequently stored, is a major problem for the recycling of used nuclear fuel. Solid adsorbents, in particular ultra-microporous metal-organic frameworks (MOFs), could be efficient in capturing these volatile radionuclides, like ⁸⁵Kr. However, MOFs are found to be more Xe-philic than Kr and to have a similar affinity between Kr and N₂. In addition, the adsorbent needs to have good radiation stability. In order to overcome these challenges, we test a series of ultra-microporous MOFs, SIFSIX-3-M (M= Zn, Cu, Ni, Co or Fe) for their potential in ⁸⁵Kr separation and storage using a two-bed breakthrough method. These materials were found to have higher Kr/N₂ selectivity than the current benchmark materials, which lead to a notable decrease in the nuclear waste volume. The materials have been systematically studied for gamma and beta irradiation stability, which demonstrates that the metal centre in these isostructural frameworks plays a crucial role in their radiation resistance.